Hot-mix asphalt manufacturing system and method

ABSTRACT

A hot-mix asphalt manufacturing system includes a counter-flow rotary dryer having a combustion chamber, an inlet for dry ingredients, an outlet for hot-mix asphalt, and a pollution control device. The pollution control system includes a pre-filter, a cooling device and a fiber bed filter. Combustion gases from the combustion chamber are directed onto the ingredients for the hot-mix asphalt without substantial introduction of excess air or recirculated air and contact the hot-mix asphalt at a temperature substantially equal to the temperature of the combustion gases. The pollution control system removes substantially all particulates and hydrocarbons from the emissions from the hot-mix asphalt ingredients.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.09/482,608, filed Jan. 14, 2000, now U.S. Pat. No. 6,478,461, issuedNov. 12, 2002.

FIELD OF THE INVENTION

The invention pertains to a method and system for manufacturing hot-mixasphalt, and in particular to a method and system for manufacturinghot-mix asphalt including recycled asphalt products.

BACKGROUND OF THE INVENTION

The present invention relates to a transportable hot-mix asphaltmanufacturing system and method, and more specifically, to a hot-mixmanufacturing system that is relatively compact and transportable tosites where the hot-mix asphalt is to be manufactured. The presentinvention also relates to compact pollution control systems andpollution control methods for a hot-mix asphalt manufacturing system.

While techniques and systems for manufacturing hot-mix asphalt aregenerally known, typically the systems used to manufacture the hot-mixasphalt include large, cumbersome components that must remain stationaryand that are not easily disassembled and/or transported should it becomenecessary to manufacture the hot-mix asphalt at another location. Anexample of such large, cumbersome components is the typical conventionalrotary dryer and its associated pollution control equipment.

Asphalt plants with rotary dryers are well-known in the art. Suchasphalt plants, however, tend to suffer from at least one of severaldisadvantages. Among the disadvantages are that: 1) they areexcessively, complex, large or bulky and cannot be transported easily toa location where the hot-mix asphalt is needed, 2) they use excessivelyexpensive, complicated, and/or large pollution control devices (some ofwhich require frequent maintenance and monitoring), and/or 3) they arenot compatible with recycled asphalt products (RAP) or cannot acceptcommingled RAP and virgin asphalt aggregates.

Conventional rotary dryers typically use cyclones, knock-out boxes,large bag houses, and/or other space-consuming pollution control devicesto process the emissions from the rotary dryers. Still other rotarydryers use expensive and/or complicated thermal oxidizers, indirectheating systems where the RAP aggregate is not exposed to the heatedair, or a second rotary dryer into which the polluted exhaust gases areinserted and diluted or burned. Notably, thermal oxidizer-based systemstend to be very expensive, bulky, and have large operating costs becauseof their high energy requirements. Indirect heating systems tend to bethermodynamically inefficient, expensive to build, and very limited inproduction rates. Systems that depend on a second rotary dryerdisadvantageously prevent one rotary dryer from being used withoutanother.

The space-consuming pollution control devices typically are not easy todisassemble and transport. Often transportation of such devices requiresa significant amount of disassembly and/or unusual transportationequipment and techniques. The combined weight and/or size of a typicalrotary dryer and its associated pollution control devices usuallyexceeds the size and/or weight restrictions of wide-load trucking in theUnited States. It therefore is difficult, if not impossible, totransport such systems using fewer than three truckloads, and withoutany complicated and time-consuming disassembly of the rotary dryer andits associated pollution control equipment. There is consequently a needin the art for a hot-mix asphalt manufacturing system, such as a rotarydryer and its associated pollution control equipment, that can betransported in fewer than three truck loads, without complicateddisassembly of the manufacturing system. Since wide-load truckingrequires official permits, escorts, and can be performed only withincertain regulatory limits, the use of wide-load trucking tends to be farmore expensive, time-consuming, and less practical than conventionaltrucking. Conventional trucking (i.e., trucking without escorts andwithout wide-load designations) can be performed, according to U.S.regulations, when the load is no larger than 8 feet, 6 inches wide by 13feet, 6 inches high by 53 feet long. The need for a transportablehot-mix asphalt manufacturing system therefore further extends to onethat, without complicated disassembly of the manufacturing system, doesnot require loads that exceed the dimensional limits of conventionaltrucking, and preferably one that can be transported in fewer than threesuch conventional truck-loads.

If a rotary dryer is capable of handling recycled asphalt product (RAP),it typically will be configured with an external combustion chamber toprotect the contents of the dryer's drum from the combustion processthat is used to generate heat. The cumulative length of the rotary dryertherefore typically includes the length of the dryer's rotatable drumplus the length of the external combustion chamber. The additionallength contributed by the combustion chamber usually precludes therotary dryer from being transported using conventional trucking in asingle truck-load. The aforementioned need to provide a readilytransportable hot-mix manufacturing system therefore extends to one thathas a rotary dryer with a combustion chamber does not contributesignificantly, if at all, to the length of the rotary dryer.

While there are some pollution control devices that are more compact,less expensive, and/or less maintenance intensive than the pollutioncontrol devices typically found on a conventional rotary dryer, suchdevices generally have not found their way into the rotary dryerindustry. Presumably, this is because of perceived incompatibilitieswith the emissions from the typical rotary dryer. Plate collectors, forexample, though they are fairly compact and inexpensive, are not used aspollution control equipment in the typical rotary dryer. It is generallyperceived that plate collectors would be overburdened and/or clogged bythe particulates in the exhaust gas of the typical rotary dryer. This isespecially so if the plate collector is to be located in therecirculated exhaust gas stream of a rotary dryer. It is generallyperceived that excessive maintenance and/or replacement of the platecollectors would be necessary if such collectors were used to removeparticulate from the recirculated exhaust gas stream.

While plate collectors can be cleaned by continuously spraying them withwater, such “wet” processing generally is not used in the context ofrotary dryers because the emissions from such rotary dryers typicallyare treated in bag houses or using other fabric-based filters. Suchbag-houses and other fabric-based filters typically are incompatiblewith condensed water. When such fabric-based filters are used, it istypically necessary that any moisture in the filtered emissions remainin the vapor state.

Likewise, fiber bed filters are not generally used to treat thepollution from the typical hot-mix rotary dryer. Presumably, this is, inpart, because of the temperature limitations imposed by the use of suchfiber bed filters. The typical fiber bed filter is not compatible withhot emissions that exceed a temperature of about 120 degrees F.

It is not unusual for the emission temperature from a rotary dryer toexceed 200 degrees F. Since the emissions from the typical hot-mixrotary dryer far exceed the 120 degree temperature limitation, thegeneral perception in the industry of hot-mix manufacturing is thatfiber bed filters are not suitable for use as pollution controlequipment in a hot-mix rotary dryer.

While some fiber bed filters have been provided with evaporative coolingsystems, whereby water is sprayed through the emissions and evaporatesto draw heat away from the emissions, the use of such fiber bed filtersin the asphalt industry generally has been limited to treatment ofrelatively low-moisture asphalt emissions (e.g. 5 emissions from shinglemanufacturing and asphalt storage facilities) having a much lowermoisture content than the emissions from the typical hot-mix rotarydryer. While evaporative cooling can be effective with low-moistureemissions, such evaporative cooling techniques alone generally are noteffective in the context of the moisture-saturated emissions from thetypical rotary dryer. In particular, the typical emissions from therotary dryer can accept little, if any, additional moisture. Fiber bedfilters therefore, even if augmented to include evaporative coolingsystems, generally have not been used to treat the emissions from ahot-mix rotary dryer.

Another problem with conventional hot-mix asphalt manufacturing systemsand methods, relates to the restrictions imposed on their feed material.Many conventional hot-mix manufacturing cold feed systems, for example,are not compatible with recycled asphalt products (RAP). In the fewrotary dryers and associated techniques that can handle significantamounts of RAP, the RAP and virgin aggregates typically must be fed intothe rotatable drum of the rotary dryer through different inlets of thedrum. The RAP and virgin aggregates therefore cannot be commingled inthe typical system or method. Because it is generally more convenient tofeed the RAP and virgin aggregates into a rotary dryer from the samelocation and/or inlet, there is a need in the art for a hot-mixmanufacturing technique and/or system that includes a rotary dryercapable of receiving the raw materials in the form of commingled RAP andvirgin aggregates and/or in the form of 100% RAP.

SUMMARY OF THE INVENTION

It is a primary object of the present invention to overcome at least oneof the foregoing problems and/or satisfy at least one of the foregoingneeds by providing a transportable hot-mix asphalt manufacturing systemand method, a method and system for treating emissions from a hot-mixasphalt manufacturing system, and a method and system for treatingrecirculated gases in a hot-mix asphalt manufacturing system.

To achieve these and other objects, the present invention provides atransportable hot-mix asphalt manufacturing system comprising a rotarydryer and at least one pollution control device. The rotary dryer isadapted to receive and dry ingredients of hot-mix asphalt. The pollutioncontrol device(s) is (are) adapted to treat emissions from the rotarydryer so that hydrocarbons and particulates are substantially removedfrom the emissions of the rotary dryer before such emissions arereleased into a surrounding environment of the rotary dryer. Thepollution control device(s) and the rotary dryer have dimensions thatpermit use of conventional trucking to transport the rotary dryer andthe pollution control device(s) in less than three conventionaltruck-loads.

Also provided by the present invention is a counter-flow rotary dryerfor a hot-mix asphalt manufacturing system. The counter-flow rotarydryer comprises a rotatable drum, an inlet, a combustion chamber, and aheat shield. The rotatable drum has a first end and an opposite end. Theinlet is for raw ingredients of hot-mix asphalt. The inlet is located ator near the first end of the rotary dryer. The combustion chamber isinternal to the rotatable drum of the rotary dryer and is radiallyspaced apart from an inside circumferential wall of the rotatable drum,to provide a mixing zone between the combustion chamber and the insidecircumferential wall. The heat shield is adapted to protect the rawingredients of hot-mix asphalt from radiant heat developed in thecombustion chamber. The counter-flow rotary dryer is adapted to receivethe raw ingredients of hot-mix asphalt through the inlet for passagethrough the rotatable drum toward the opposite end thereof, whilecombustion gases from the combustion chamber flow substantially from theopposite end of the rotary dryer toward the first end to heat and drythe raw ingredients.

Also provided by the present invention is a rotary dryer for a hot-mixasphalt manufacturing system, wherein the rotary dryer comprises arotatable drum, a combustion chamber, a recirculator, and a platecollector. The rotatable drum has a first end and an opposite end. Thecombustion chamber is located at or near the opposite end. Therecirculator is adapted to recirculate some combustion gases at thefirst end back tdthe combustion chamber at or near the opposite end. Theplate collector is adapted to substantially remove particulates fromcombustion gases that are recirculated by the recirculator.

According to another aspect of the present invention, a hot-mix asphaltmanufacturing system can be provided with a rotary dryer and at leastone pollution control device that includes a fiber bed filter. Therotary dryer is adapted to receive and dry ingredients of hot-mixasphalt. The pollution control device(s) is (are) adapted to treatemissions from the rotary dryer so that hydrocarbons and particulatesare substantially removed from the emissions of the rotary dryer beforesuch emissions are released into a surrounding environment of the rotarydryer.

Also provided by the present invention is a transportable hot-mixasphalt manufacturing system comprising a counter-flow rotary dryer, aplate collector, a fiber bed filter, a cooling zone, a heat exchanger, acoolant recovery mechanism, and a plate collector sprayer. Thecounter-flow rotary dryer is adapted to receive and dry ingredients ofhot-mix asphalt. The counter-flow rotary dryer includes a combustionchamber and a recirculator adapted to recirculate emissions from therotary dryer into the combustion chamber. The combustion chamber isinternal to the rotary dryer and is radially spaced apart from an insidecircumferential wall of the rotary dryer, to provide a mixing zonebetween the combustion chamber and the inside circumferential wall. Theplate collector is adapted to remove particulates from emissions thatare recirculated into the combustion chamber by the recirculator. Thefiber bed filter is adapted to treat emissions from the rotary dryer sothat hydrocarbons and particulates are substantially removed from theemissions of the rotary dryer before such emissions are released into asurrounding environment of the rotary dryer. The cooling zone is locatedbetween the rotary dryer and the fiber bed filter. The cooling zone isadapted to cool the emissions from the rotary dryer enough that suchemissions achieve a temperature that is compatible with the fiber bedfilter. The cooling zone includes at least one coolant sprayer adaptedto spray a coolant through the emissions as such emissions pass throughthe cooling zone. The heat exchanger is connected at least indirectly tothe coolant sprayer. The heat exchanger is adapted to remove heat fromthe coolant before the coolant is sprayed through the cooling zone. Thecoolant recovery mechanism is connected at least indirectly to the heatexchanger. The coolant recovery mechanism is adapted to recover andrecirculate through the heat exchanger the coolant after it has beensprayed through the cooling zone. The plate collector sprayer is adaptedto spray the plate collector so that at least some of the particulatesremoved by the plate collector from the emissions are cleaned away fromthe plate collector. The hot-mix asphalt manufacturing system hasdimensions that permit use of conventional trucking to transport thehot-mix asphalt manufacturing system in less than three conventionaltruck-loads.

The present invention also provides a method of manufacturing hot-mixasphalt. The method comprises the steps of providing a rotary dryer andat least one pollution control device, with dimensions that permit useof conventional trucking to transport the rotary dryer and the pollutioncontrol device(s) in less than three conventional truck-loads, feedingprimary ingredients of hot-mix asphalt into the rotary dryer, drying theprimary ingredients of hot-mix asphalt in the rotary dryer, and treatingemissions from the rotary dryer so that hydrocarbons and particulatesare substantially removed from the emissions of the rotary dryer beforesuch emissions are released into a surrounding environment of the rotarydryer.

The step of providing the rotary dryer and the pollution controldevice(s) preferably includes configuring the pollution controldevice(s) and/or the rotary dryer so that its length is less than orequal to about 53 feet, its height is less than or equal to about 13feet, 6 inches, and its width is less than or equal to about 8 feet, 6inches.

Also provided by the present invention is a method of manufacturinghot-mix asphalt, wherein the method comprises the step of providing arotary dryer that includes 1) a rotatable drum having a first end and anopposite end, 2) an inlet for primary ingredients of hot-mix asphalt,the inlet being located at or near the first end of the rotary dryer, 3)a combustion chamber that is internal to the rotatable drum of therotary dryer and that is radially spaced apart from an insidecircumferential wall of the rotatable drum, to provide a mixing zonebetween the combustion chamber and the inside circumferential wall, and4) a heat shield adapted to protect the primary ingredients of hot-mixasphalt from radiant heat developed in the combustion chamber. Thismethod further comprises the steps of 1) introducing primary ingredientsof hot-mix asphalt into the rotatable drum, through the inlet, 2)rotating the rotatable drum so that the primary ingredients are conveyedthrough the rotatable drum toward the opposite end thereof, whilecombustion gases from the combustion chamber flow substantially from theopposite end of the rotary dryer toward the first end to heat and drythe primary ingredients, and 3) introducing supplemental ingredientsinto the mixing zone of the rotary dryer so that the supplementalingredients are mixed with the primary ingredients after the primaryingredients have substantially completed a drying treatment in therotary dryer.

Preferably, the supplemental ingredients are selected from the group ofsupplemental ingredients consisting of asphalt cement, rejuvinators,plasticizers, and combinations thereof.

The present invention also provides a method of treating recirculatedgases in a hot-mix asphalt manufacturing system. The method comprisesthe steps of directing recirculated gases from a rotary dryer through aplate collector, and removing particulates from the recirculated gasesas the particulates are propelled, by the recirculated gases, into theplate collector.

Also provided is a method of treating emissions from a hot-mix asphaltmanufacturing system. The method comprises the steps of directingemissions from a rotary dryer to a fiber bed filter, and substantiallyremoving hydrocarbons and particulates from those emissions at the fiberbed filter before such emissions are released into a surroundingenvironment of the rotary dryer.

The present invention also provides a method of manufacturing hot-mixasphalt wherein the method comprises the steps of feeding primaryingredients of hot-mix asphalt into a rotary dryer, drying the primaryingredients of hot-mix asphalt in the rotary dryer, in a counter-flowmanner, treating emissions from the rotary dryer by passing theemissions through a fiber bed filter so that hydrocarbons andparticulates are substantially removed from the emissions of the rotarydryer before such emissions are released into a surrounding environmentof the rotary dryer, recirculating emissions from the rotary dryer backinto a combustion chamber of the rotary dryer, and removingparticulates, using a plate collector., from the emissions that arerecirculated back into the combustion chamber.

Preferably, the emissions being processed according to any of theforegoing methods or systems are subjected to coalescent filtrationand/or Brownian diffusion filtration in a fiber bed filter. In addition,the primary ingredients that are processed in any one of the foregoingsystems or according to any one of the foregoing methods can include100% recycled asphalt product (RAP) or commingled RAP with virginaggregates. The above and other objects and advantages will become morereadily apparent when reference is made to the following descriptiontaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a rotary dryer accordingto a preferred embodiment of the present invention.

FIG. 2 is a fragmentary perspective view of burner-equipped end of therotary dryer shown schematically in FIG. 1.

FIG. 3 is a perspective view of the rotary dryer shown in FIG. 2, takenfrom an end of the rotary dryer opposite to where the burner is located.

FIG. 4 is a side elevation view of a pollution control device accordingto a preferred embodiment of the present invention.

FIG. 5 is a plan view of the pollution control device shown in FIG. 4.

FIG. 6 is a side view of a combustion chamber of the rotary dryer shownin FIGS. 1-3, according to a preferred embodiment of the presentinvention.

FIG. 7 is a cross-sectional view of the combustion chamber shown in FIG.6, taken along line XII—XII in FIG. 6.

FIG. 8 is a fragmentary perspective view of a drum of the rotary dryershown in FIGS. 1-3, wherein the v/all of the drum is partially omittedfrom the view to show an arrangement of flights in the drum, accordingto a preferred embodiment of the present invention.

FIG. 9 is a perspective view of a plate collector in the rotary dryershown in FIGS. 1-3, according to a preferred embodiment of the presentinvention.

FIG. 10 is a fragmentary elevation view of a rotary dryer exhaust ductthat houses the plate collector shown in FIG. 9, according to apreferred embodiment of the present invention.

FIG. 11 is a fragmentary plan (or top) view of the rotary dryer exhaustduct shown in FIG. 10.

FIG. 12 is a block diagram of a coolant circuit according to a preferredembodiment of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

With reference to FIGS. 1-6, a transportable hot-mix asphaltmanufacturing system will be described according to a preferredembodiment of the present invention. The hot-mix asphalt manufacturingsystem comprises a rotary dryer 12 (shown in FIGS. 1-3) and at least onepollution control device 14 (shown in FIGS. 4 and 5).

The rotary dryer 12 is adapted to receive ingredients of hot-mix asphaltand to perform a drying process on such ingredients. Preferably, therotary dryer 12 is a counter-flow rotary dryer 12. The term“counter-flow” is understood to mean that the materials being dried inthe rotary dryer 12 generally flow, or are conveyed, in one direction,whereas the emissions and/or by-products of the drying process flow inan opposite direction.

The rotary dryer 12 preferably includes a burner 16 and a rotatable drum18 having a first end 20 and an opposite end 22. The opposite end 22 isshown in FIGS. 1 and 2, whereas the first end 20 is shown in FIGS. 1 and3.

An inlet 24 for raw or primary ingredients of the hot-mix asphaltpreferably is located at or near the first end 20 of the rotatable drum18. An outlet 26 for the hot-mix asphalt manufactured by the rotarydryer 12 can be located at or near the opposite end 22.

The raw or primary ingredients can be brought to the inlet 24 andintroduced into the rotatable drum 28 using a conventional conveyorsystem 27 (e.g., a belt-type conveyor). The conveyor system 27 is notshown in FIG. 3 so that other structural components of the rotary dryer12 can be visualized more easily in that drawing.

The rotary dryer 12 preferably includes a combustion chamber 28 in whichthe burner 16 provides combustion. The combustion chamber 28 preferablyis internal to the rotatable drum 18 of the rotary dryer 12 and isradially spaced apart from an inside circumferential wall 30 of therotatable drum 18. The radial spacing advantageously provides a mixingzone 32 between the combustion chamber 28 and the inside circumferentialwall 30. Supplemental ingredients (or additives) can be introduced intothe mixing zone 32 of the rotary dryer 12 so that the supplementalingredients are mixed with the primary ingredients after the primaryingredients have substantially completed a drying treatment in a dryingzone 34 of the rotary dryer 12. The supplemental ingredients, forexample, can include asphalt cement, rejuvinators, plasticizers, and/orcombinations thereof. Since the tubular walls 42 of the combustionchamber 28 remain stationary (i.e., they do not rotate with the drum18), plumbing (not shown) for the supplemental ingredients can beprovided through or along the wall 42 of the combustion chamber 28.Pumps and metering equipment for the supplemental ingredients can belocated outside of the rotary drum 18 and can be connected to anexternal plumbing connection. A nozzle directed toward the mixing zone32 can be mounted at the internal end of the plumbing, to expel thesupplemental ingredients into the mixing zone 32. Using such anarrangement, the supplemental ingredients can be metered outside of therotatable drum 18, can be pumped into the plumbing, and can be expelledinto the mixing zone 32 by the nozzle.

Downstream (with respect to ingredient flow) of the mixing zone 32, thehot-mix asphalt manufactured by the rotary dryer 12 is allowed to dropthrough the outlet 26 and onto a hot-mix conveyor system 36. In FIG. 2,the hot-mix conveyor system 36 is not shown so that other structuralcomponents of the rotary dryer 12 can be visualized more easily in thatdrawing.

Since the combustion chamber 28 is internal to the rotatable drum 18,its length contributes little, if anything, to the overall length of therotary dryer 12. This advantageously allows the rotary dryer 12 to beprovided in a more compact structure than might otherwise be possible.

A heat shield 40 can be provided to protect contents of the rotary dryer12 from radiant heat produced in the combustion chamber 28. The heatshield 40 and the tubular walls 42 of the combustion chamber 28preferably are made of stainless steel (e.g., alloy 309).

In operation, the raw or primary ingredients of the hot-mix asphalt arereceived through the inlet 24 for passage through the rotatable drum 18toward the opposite end 22. At the same time, combustion gases from thecombustion chamber 28 flow substantially from the opposite end 22 of therotary dryer 12 toward the first end 20 to heat and dry said rawingredients.

The counter-flow rotary dryer 12 preferably is adapted to manufacturehot-mix asphalt when the primary (or raw) ingredients received throughthe inlet 24 include 100% recycled asphalt products (RAP), or virginaggregates commingled with recycled asphalt products (RAP). Use of suchprimary ingredients is facilitated by keeping the flame in thecombustion chamber 28 from impinging upon the primary ingredients (e.g.,by providing the combustion chamber 28 with walls 42 and the heat shield40).

The system preferably includes a recirculator 44. The recirculator 44 isadapted to recirculate emissions (or combustion gases) from the firstend 20 of the rotary dryer 12 back into the combustion chamber 28,preferably, at or near the opposite end 22. The recirculator 44 includesa recirculator duct 46 extending from the first end 20 of the rotarydryer 12 to the opposite end 22. A damper 48 and recirculation fan 50are located along the recirculator duct 46. The damper can be locatedanywhere along the length of the recirculator duct 46, or alternatively,as shown in FIG. 2, can be located at the intake of the fan 50. Therecirculation fan 50 draws emissions from the first end 20 of the rotarydryer 12 into the recirculator duct 46 and pushes such emissions intothe combustion chamber 28. The orientation of the damper 48 can bemodulated to provide a desired volume of flow through the recirculationduct 46. The recirculated emissions (or combustion gases) can be mixedand appropriately proportioned with ambient air that is drawn into thecombustion chamber 28 via intakes 52, to achieve efficient combustion inthe combustion chamber 28,

FIG. 6 is a side view of the combustion chamber 28 according to apreferred embodiment of the present invention. FIG. 7 is across-sectional view taken along line XII—XII in FIG. 6. Connectedbetween the recirculation duct 46 (or the recirculation fan 50) and thecombustion chamber 28 is a recirculation transition duct 54. Therecirculation transition duct 54 provides a flow size adjustment fromthe size of the recirculation duct 46 or fan 50 to the size of therecirculation entrance 56 to the combustion chamber 28.

A deflector plate 58 can be mounted so that it extends from therecirculation transition duct 54 into the combustion chamber 28. Thedeflector plate 58 serves to redirect the flow of emissions toward thecombustion chamber 28 from the recirculation transition duct 54. Aflange 60 is provided at least partially around the exterior of thewalls 42 of the combustion chamber 28. The flange 60 facilitatesmounting and positioning of the combustion chamber 28 to the rotarydryer 12.

The recirculation transition duct 54, the flange 60, and any portion ofthe combustion chamber that extends to the left of the flange 60 in FIG.6 preferably are mounted outside of the rotatable drum 18. Since thesecomponents do not engage the ingredients in the rotatable drum 18, theycan be made of mild steel, instead of stainless steel.

As illustrated in FIG. 6, the shield 40 preferably is secured to the end62 of the tubular walls 42 by several tabs 64 (two of which are shown inFIG. 6). The tabs 64 extend radially inv/ardly from the walls 42 andforward (toward the first end 20) as well. Preferably, the tabs 64 arearranged so that the heat shield 40 is about 10 inches forward of theend 62 of the tubular walls 42.

FIG. 8 is a fragmentary perspective view of the drum 18 of the rotarydryer 12, wherein the wall 30 of the drum 18 is partially omitted fromthe view to show the interior of the dmm 18. As shown in FIG. 8, thetabs 64 preferably are spaced apart from one another to define openings66 between the shield 40 and the walls 42. These openings 66 allow thecombustion gases generated in the combustion chamber 28 to flow out fromthe combustion chamber 28 and into the drying zone 34 of the rotarydryer 12.

The recirculation provided by the recirculator 44 has the beneficialeffect of cooling the byproducts of combustion without significantlydecreasing the rotary dryer's overall efficiency. Preferably, the damper48 is modulated so that the combustion gases exiting the combustionchamber 28 are at a temperature of about 1,000 to 1,200 degrees F., andthe rest of the rotary dryer 12 is configured and operated so that thehot-mix asphalt exiting the mixing zone 32 through the outlet 26 has atemperature of about 300 degrees F. An exemplary flow rate of theemissions through the recirculation duct 44 is about 10,000 actual cubicfeet per minute (A.C.F.M.).

As illustrated in FIG. 1, a plate collector 70 can be provided at therecirculator 44. The plate collector 70 can be provided as part of, inassociation with, or separate from, the pollution control device 14. Theplate collector 70 is adapted to remove particulates from emissions (orcombustion gases) that are recirculated into the combustion chamber 28by the recirculator 44. The plate collector 70 preferably removes fromthe emissions (or combustion gases) that are being recirculated by therecirculator 44, at least about 90% of the particulates suspended insuch emissions (or combustion gases). As shown in FIG. 9, a platecollector 70 can be configured from plates 72 that are commerciallyavailable, for example, from Otto York. Each plate 72 in a platecollector 70 has major surfaces 74 that undulate. The plates 72 arespaced from one another such that an undulating flow path 76 is createdbetween each pair of the plates 72. Emissions flowing between the plates72 must follow the undulating paths 76. Particulates in the emissions,however, tend to collide with, and collect on, the undulating surfaces74 of the plates 72, rather than follow the entire undulating flow paths76.

As shown schematically in FIG. 1, a plate collector sprayer 80 can beprovided to spray the plate collector 70 so that at least some of theparticulates removed by the plate collector 70 from the emissions (orcombustion gases) are cleaned away from the plate collector 70.Preferably, the plate collector sprayer 80 is adapted to spray water onthe plate collector 70 so that the water strikes the particulates andfalls away from the plate collector 70, carrying at least some of theparticulates away from the plate collector 70. While the plate collectorsprayer 80 can be mounted to the rotary dryer 12, it is understood thatit need not be fixed permanently to the dryer 12. An access hatch 82,for example, can be provided near the plate collector 70, as shown inFIG. 3. Whenever it is desirable or necessary to spray the platecollector 70 using an independent sprayer, access can be gained throughthe access hatch 82.

As illustrated in the perspective view of FIG. 3, the fragmentaryelevation of FIG. 10, and the fragmentary top view of FIG. 11, the platecollector 70 preferably receives the emissions from the rotary dryer 12via a rotary dryer exhaust duct 84. The rotary dryer exhaust duct 84 isconnected between the first end 20 of the rotary dryer 12 and the platecollector 70. Not all of the emissions from the rotary dryer 12 arerecirculated by the recirculation duct 46. The excess emissions at thefirst end 20 of the rotary dryer 12 (i.e., the emissions in excess ofwhat is to be recirculated) are directed into a pollution control duct86 by the rotary dryer exhaust duct 84. The pollution control duct 86 isconnected between the entrance 88 to the plate collector 70 and theaforementioned pollution control device(s) 14. The excess emissionstherefore are treated by the pollution control device(s) 14.

With reference to FIGS. 4 and 5, the pollution control device(s) 14 is(are) adapted to treat emissions from the rotary dryer 12 so thathydrocarbons and particulates are substantially removed from theemissions of the rotary dryer 12 before such emissions are released intoa surrounding environment of the rotary dryer 12. Hereinafter, thepollution control device(s) 14 will be referred to in singular form,though it is understood that more than one such device 14 can beprovided.

Preferably, the pollution control device 14 includes a fiber bed filter90. The fiber bed filter 90 preferably is configured to providecoalescent filtration of emissions from the rotary dryer 12. Thecoalescent filtration preferably is achieved by subjecting the emissionsfrom the rotary dryer 12 to Brownian diffusion filtration. Fiber bedfilters suitable for use in the exemplary pollution control device 14shown in FIGS. 4 and 5 are commercially available, for example, fromAdvanced Environmental Systems. The pollution control device 14preferably includes a cooling zone 92 adapted to cool the emissions fromthe rotary dryer 12 enough that such emissions achieve a temperaturethat is compatible with the fiber bed filter 90. A partition 94separates the cooling zone 92 from the fiber bed filter 90. Thepartition 94, however, stops short of the top 96 of the pollutioncontrol device 14 so that emissions treated in the cooling zone 92 canenter the fiber bed filter 90 through an opening between the partition94 and the top 96.

The cooling zone 92 preferably includes at least one coolant sprayer 98adapted to spray a coolant 100 into the emissions as such emissions passthrough the cooling zone 92. The spray of coolant 100 advantageouslyreduces the temperature of the emissions and causes the majority of theremaining uncondensed hydrocarbons to become condensed. The spray ofcoolant 100 also encourages coalescing of the submicron particulates tobegin. The cooling zone 92 can be provided with a cyclonic plate 102adapted to induce a cyclonic flow of the emissions in the cooling zone92. The cyclonic plate 102 can include a central hub 104 and a pluralityof blades 106 that extend radially out from the hub 104. The blades 106preferably are angled so as to induce the desired cyclonic flow of theemissions in the cooling zone 92. The cyclonic flow in the cooling zone92 provides aggressive contact between the emissions and the coolant100. This, in turn, tends to enhance exposure of the emissions to thecoolant spray and thereby enhances the cooling and condensation effectsprovided thereby. It also enhances the likelihood that particulates inthe emissions will engage coolant droplets and/or the wet walls 108 ofthe cooling zone 92, and that such particulates will coalesce and fallwith the coolant droplets or with the flow of coolant along the walls108 of the cooling zone 92, into a coolant recovery mechanism 110 to bedescribed hereinafter.

The cooling zone 92 also can include an air introduction port 112through which air cooler than the emissions is introduced into theemissions after the cooling zone 92 to further cool and/or dilute theemissions prior to entering the fiber bed filter 90. Preferably, adilution air damper 114 is provided in the air introduction port 112.The dilution air damper 114 can be selectively opened and closed toregulate the flow of air through the introduction port 112. This, inturn, can be used to ensure that enough ambient air enters the flow ofemissions to ensure that the temperature of the emissions reaching thefiber bed filter 90 remains within acceptable limits (e.g., at about 120degrees F.). The dilution air damper 114 in this regard can becontrolled in response to a temperature signal from a temperaturesensor, such as a thermocouple located in the stream of emissionsflowing into the fiber bed filter 90.

Inasmuch as some larger particulates (above the submicron range ofsizes) may pass through the coolant spray without becoming engaged to acoolant droplet and some droplets may be swept up in the flow ofemissions, a pro-filter 116 can be located between the coolant spray andthe fiber bed filter 90, preferably between the coolant spray and theair introduction port 112. To avoid the expense of filter replacement,the pro-filter 116 can be provided in the form of a washable platecollector 116. Since the washable plate collector 116 is capable ofstopping the coarse, sticky particulates and coolant droplets, ade-misting function is served by the pre-filter 116 and the surfaceloading of the fiber bed filters 90 is advantageously reduced. Thisreduction in surface loading advantageously translates into a longerfiber bed filter life.

Preferably, the coolant sprayer(s) 98 is connected to a heat exchanger118 (shown in FIG. 5). The heat exchanger 118 is adapted to remove heatfrom the coolant 100 before the coolant 100 is sprayed through thecooling zone 92. This can be done by feeding the coolant 100 through aradiator-like vessel 120 with heat dissipating fins, while ambient airis passed over the vessel 120 or through openings in the vessel 120.Preferably, a heat exchanger 118 is provided with a fan 122 that forcesair over the surface of the vessel 120 and through any openings in thevessel 120. Heat from the coolant 100 thereby is transferred to theambient air and is dissipated into the surrounding environment. Thecoolant 100 then exits the vessel 120 at a lower temperature than whenit entered.

The heat exchanger 118 can be connected to the coolant recoverymechanism (or sump) 110 which is adapted to recover the coolant 100after it has been sprayed through the cooling zone 92 and recirculatethe coolant 100 through the heat exchanger 118. The coolant recoverymechanism 110 preferably includes a recirculation pump 130 and a motor132 that drives the recirculation pump 130.

Preferably, as shown in FIG. 12, this same coolant recovery mechanism(or sump) 110 is fluidly connected at least indirectly to the platecollector sprayer 80 so that the coolant 100 used in the cooling zone 92also is supplied to the plate collector sprayer 80 and is sprayed by theplate collector sprayer 80 to clean particulates away from the platecollector 70. The coolant 100 preferably is water. Other coolants,however, can be used. Preferably, the coolant recovery mechanism (orsump) 110 also recovers and recirculates the coolant (or water) 100 thatthe plate collector sprayer 80 sprays onto the plate collector 70. Sincethe washable plate collector 116 that can be used as the pre-filter 116is located above the coolant sprayer 98, the run-off from washing of thev/ashable plate collector 116 also can be collected by the coolantrecovery mechanism (or sump) 110. In this regard, washing of thewashable plate collector 116 can be performed using the same coolant(e.g., water) 100 that is used by the coolant sprayer 98.

Generally, recovery and recirculation of the coolant 100 is desirablebecause it minimizes coolant (e.g., water) consumption. As the coolant(e.g., water) 100 evaporates, it can be added automatically by asuitable coolant (e.g., water) level-responsive re-fill valve WV.

Depending on local regulations, there may be no need to recover thecoolant 100. In some cases, for example, it may be legal and practicalto dispose of the particulate-containing coolant 100 in a sewer orwastewater treatment facility.

Since the coolant (e.g., water) 100 carries particulates away from thecooling zone 92, from the plate collector 70 and/or from the washablepre-filtering plate collector 116, a particulate removal device 140 canbe connected at least indirectly to the coolant recovery system 110. Theparticulate removal device 140 removes particulates entrained in thecoolant 100 from the coolant 100 prior to the coolant 100 being sprayedby the plate collector sprayer 80 and/or by the coolant sprayer 98.

A hydra clone 140 can be used as the particulate removal device 140.Other particulate removal devices and/or techniques, however, can beused. The particulates that are removed by the particulate removaldevice 140 can be discarded or alternatively can be fed back to therotary dryer 12. As illustrated in FIG. 12, the particulates can bestored in a stockpile at the output from the hydraclone.

Preferably, as illustrated in FIG. 8, the inside wails 30 (which arepartially omitted in this view) of the drum 18 are provided withnumerous flights 150 of teeth 152. Notably, in the exemplary embodimentof FIG. 8, three sections of flights 150 are provided. One section 154is located for rotation through the mixing zone 32. A second section 156is located in the drying zone 34, far from the mixing zone 32. Locatedbetween the first and second sections 154, 156, is the third section 158of flights 150.

Preferably, the spacing between the flights 150 in the first and thirdsections 154,158 is larger than the spacing between the flights 150 inthe second section 156. In addition, the teeth 152 of each section canbe bent toward the walls 30. In the exemplary embodiment shown in FIG.8, the teeth 152 of each flight 150 in the second section 156 are bentcloser toward the walls 30 of the drum 18 than the teeth 152 in thefirst and third sections 154, 158. Likewise, the teeth 152 of eachflight 150 in the third section 158 are bent closer toward the walls 30of the drum 18 than the teeth 152 in the first section 154. Thedifferences between the teeth 152 and flight 150 arrangements in thedifferent sections 154,156,158 are consistent with providing more of alifting-and-dropping action in the drying zone 34 and more of a tumblingaction in the mixing zone 32. Preferably, the rotary dryer 12 is rotatedat a sufficient speed to provide aggressive veiling of the primaryingredients in the rotary dryer 12 (i.e., aggressive lifting anddropping of the ingredients so that they are spread out and exposedaggressively to the combustion gases). When this aggressive veiling iscombined with the counter-flow operation of the rotary dryer 12 and therecirculation of emissions provided by the recirculator 44, theresulting hot-mix manufacturing system produces emissions thatadvantageously have a relatively low exhaust gas temperature. Theexemplary configuration shown in FIGS. 1-12 and described above, forexample, can be configured and operated so that the emissions exit therotary dryer 12 at a temperature of about 200 to 212 degrees F.

Such a reduction in emission temperatures provides two primary benefits.The first benefit is a reduction in the amount of energy (or heat) lostthrough the emissions. This, in turn, enhances the overall efficiency ofthe hot-mix asphalt manufacturing system. It also brings the emissiontemperatures closer to the temperatures that are compatible withexisting cost-effective and practical fiber bed filters, especiallythose that effectively remove the particulates and/or hydrocarbons usingcoalescent filtration and/or Brownian diffusion filtration. The lowerexit temperature makes it far more practical to further cool (using theaforementioned coolant spray and/or introduction of ambient air throughthe air introduction port 112) the emissions to temperatures (e.g.,about 120 degrees F.) that are compatible with the exemplary fiber bedfilter 90 described above.

A second benefit is that the hydrocarbon compounds that evaporate offfrom the asphalt cement-coated primary ingredients in the hotter zonesof the dryer 12 begin to condense as they exit the rotary dryer 12.These hydrocarbons are relatively long-chain hydrocarbons and condenseout from the emissions at temperatures above 120 degrees F. Many suchhydrocarbons will condense out in the rotary dryer 12 to form an aerosolin the emissions. The condensation of hydrocarbons makes their removalfrom the emissions more practical because they can be removed using theaforementioned coalescent fiber bed filters 90. In particular, theaerosol strikes the fiber bed filter 90 and coalesces thereon. Ascoalescing continues, the collection of hydrocarbons becomes enough toovercome surface tension and the coalesced hydrocarbons drop from thefiber bed filter 90 for collection and disposal.

With reference to FIGS. 4 and 5, the fiber bed filter 90 can be definedby a plurality of fiber bed filter tubes 160. Preferably, the filtertubes 160 are arranged vertically and substantially parallel to oneanother. Each filter tube 160 is made of densely packed fiber bed filtermaterial capable of coalescing submicron aerosol. The exterior of eachfilter tube 160 is exposed to the incoming cooled and/or dilutedemissions from the cooling zone 92.

As coalescing of the aerosol continues, the coalesced aerosol begins todrop from the tubes 160 onto a floor 162 of the intake portion 164 ofthe filter bed housing 166. Notably, the floor 162 is slanted toward afilter bed sump 168 so that the run-off from the fiber bed filter 90 canbe collected and appropriately treated and/or discarded. Generally, itis desirable to treat the run-off from the fiber bed filter 90separately from the coolant (e.g., water) 100 because of its highcontent of hydrocarbons. Alternatively, the floor 162 can be slantedtoward the coolant recovery mechanism 110 so that the run-off from thefiber bed filter 90 is collected and processed along with the recoveredcoolant (e.g., water) 100.

The inside of each fiber bed filter tube 160 has a closed bottom end 169and is fluidly connected to a clean air exhaust chamber 170 of the fiberbed filter 90. The clean air exhaust chamber 170, in turn, is connectedto a clean air exhaust duct 172. The emissions therefore are filtered bypassing through the walls of the tubes 160, from an outside surface of atube 160 to the inside surface thereof. The filtered emissions then flowthrough the inside of the tube(s) 160 toward the clean air exhaustchamber 170 and then into the clean air exhaust duct 172.

A clean/dirty partition 176 separates the clean air exhaust chamber 170from the intake portion 164 of the housing 166. The clean/dirtypartition 176 has a horizontal portion 178 that has holes aligned withthe insides of the tubes 160, so that the insides of the tubes 160fluidly communicate with the clean air exhaust chamber 170.

A filter fan 180 and filter damper 182 can be provided at the fiber bedfilter 90 to induce and control, respectively, the flow of emissionsthrough the fiber bed filter 90. The clean air from the clean airexhaust duct 172 is drawn into the fan 180 and expelled through anexhaust stack 184. The fan 180 can be driven directly by a motor 186, oralternatively, as shown in FIGS. 4 and 5, can be driven by a belt/pulleyarrangement 188 that, in turn, is driven by the motor 186. Preferably, abelt guard 190 is provided at least partially around the belt/pulleyarrangement 188.

The motor 186 that turns the filter fan 180 can be operated at arelatively constant frequency level, and the damper 182 can be modulatedto control the flow rate of emissions through the fiber bed filter 90.This arrangement has the advantage that the fan 180 requires no complexcontrol and/or drive circuitry. The fan 180 simply operates at arelatively constant speed, with the damper 182 providing the desiredcontrol in flow rate.

Generally, the filtration efficiency of the fiber bed filter 90 remainsconstant as the filter 90 becomes fouled. The pressure differencerequired across the filter 90 to maintain the same How rate, however,increases as the filter 90 becomes fouled. The filter 90 typicallyremains useful until the requisite difference in pressure across thefilter 90 increases beyond the capabilities of the fan 180 or its motor186. When the requisite difference in pressure exceeds the capabilitiesof the fan 180 and/or motor 186, the filter tubes 160 can be replaced.

In embodiments that have a damper 182 and fan 180 arrangement, therelatively constant flow rate of emissions through the fiber bed filter90 is maintained by keeping the damper 182 only slightly open when thefilter 90 is new and by gradually moving the damper 182 toward a fullyopen position as the pressure difference across the filter 90 increaseswith fouling of the filter 90 over a long period of time.

Alternatively, compensation for the increasing difference in pressurerequired across the filter 90 can be provided without the damper 182, byproviding an adjustable-speed filter fan 180 and/or motor 186. Avariable frequency fan drive, for example, can be connected to thefilter fan 180 or motor 186. The variable frequency fan drive modulatesthe speed of the fan motor 186 to compensate for increases in therequired pressure difference across the filter 90. The fan 90, in thisregard, can be driven at a faster rate as the filter 90 becomes fouled.

While arrangements with the adjustable-speed fan 180 may be moreexpensive to initially implement than the damper 182/fan 180arrangements (e.g., because they require variable frequency fan drive orsome other mechanism for driving the fan 180 in such a way that thepressure difference across the filter 90 increases), it will beappreciated that the power requirements of the fan 180, over time, aresignificantly reduced. The reductions in power requirements are realizedbecause the fan 180 can be slowed down when the filter 90 is new orrelatively unfouled, and have its power requirements increased only asneeded to compensate for fouling of the filter 90.

Regardless of whether the pollution control device 14 is implementedwith a damper 182/fan 180 arrangement, an arrangement with anadjustable-speed fan, or a combination of both, it will be appreciatedthat the speed and/or damper 182 can be modulated (automatically ormanually) in response to a signal from a pressure transducer PT locatedbetween the cooling zone 92 and the fiber bed filter 90 or located atthe intake 192 to the pollution control device 14. The signal from thepressure transducer PT indicates the intake pressure of the fiber bedfilter 90 or pollution control device 14, and therefore also provides arelatively accurate indication of the rate at which emissions are beingdrawn through the fiber bed filter 90. Alternatively, the speed and/ordamper 182 can be modulated (automatically or manually) by a signal froma pressure sensor at the mixing zone 32 of the rotary dryer 12. Thesignal from the pressure sensor at the mixing zone 32 can be used togradually open the damper 182 as the pressure detected in the mixingzone 32 increases beyond a predetermined desired negative pressure,toward ambient pressure. By contrast, the damper 182 is gradually closedif the pressure in the mixing zone 32 becomes more negative than thepredetermined desired negative pressure, according to the signal fromthe pressure sensor. The rate at which emissions are drawn through therotary dryer 12 therefore can be controlled by suitably controlling thedamper 182 and/or fan 180 speed in response to the pressure in themixing zone 32.

When it is practical to reduce the flow rate of emissions, a longerfiber bed filter life can be provided by partially closing the damper182 and/or by reducing the speed of the fan 180. This, in turn,decreases the flow of emissions through the fiber bed filter 90 andincreases the life of the filter tubes 90. The time between maintenanceand/or replacement of the filter 90 therefore can be expanded byreducing the flow rate of emissions. An advantage of the fiber bedfilters 90 is that such reductions in flow rate have no negative impacton the filtering efficiency.

Preferably, the pollution control device 14 and the rotary dryer havedimensions that permit use of conventional trucking to transport therotary dryer 12 and the pollution control device 14 in less than threeconventional truck-loads. The pollution control device 14 and/or therotary dryer 12, in this regard, preferably are configurable so thateach has a length that is less than or equal to about 53 feet, a heightthat is less than or equal to about 13 feet, 6 inches, and a width thatis less than or equal to about 8 feet, 6 inches. The rotary dryer 12therefore can be transported conveniently using conventional trucking toa site where the hot-mix asphalt is needed, as can the exemplarypollution control device 14. An additional truck load can be used totransport a supply facility to the same site. The supply facility caninclude, for example, a source of power (e.g., an electric generator), asource of fuel, and/or a source of supplemental ingredients for therotary dryer 12 and its associated pollution control device 14. Sincethere is no need to significantly disassemble the pollution controldevice 14 before it is transported, the process of putting the hot-mixmanufacturing system in operation is relatively easy. It primarilyinvolves connecting the supply facility components to the rotary dryer12 and the ducts 86 from the rotary dryer 12 to the pollution controldevice 14, and making other minor connections for power, signaltransmission, and fuel and/or water supply.

The foregoing hot-mix asphalt manufacturing system therefore makes itmuch more practical and inexpensive to set up a hot-mix asphaltmanufacturing facility at a remote site where the hot-mix asphalt isneeded. Notably, the transportable hot-mix asphalt manufacturing systemis not limited to use with virgin aggregates. It can process 100% RAP,as well as commingled RAP and virgin aggregates. This represents asignificant advance over conventional hot-mix asphalt manufacturingsystems. According to the present invention, it is now possible toprovide a hot-mix manufacturing service according to which themanufacturing facility is brought to the site where the asphalt isneeded or to a site where the raw materials are located. Significantsavings in labor and transportation costs can be realized by such asystem. The manufacturing service according to the present inventionalso can include operator services, whereby trained operators of thesystem are dispatched with the system to the site where hot-mix asphaltis to be manufactured. Alternatively, the truck loads that make up therotary dryer 12, pollution control device 14, and/or supply facility canbe leased or rented, and then located at the site where they are needed.A trained operator of the customer then would operate the system.

Using the foregoing hot-mix asphalt manufacturing system, a plantcapable of producing 800 tons per day of hot-mix asphalt for lay down orpatching can be set up virtually anywhere such a plant is desired. Thisis especially desirable in the street maintenance industry, as well asin commercial projects where significant amounts of hot-mix asphalt arebeing installed. All that is needed at the site in addition to therotary dryer 12, pollution control device 14, and supply facility, iswater (if it is not already stored in the supply facility) and aconvenient stock pile of waste asphalt. Virgin aggregates are neededonly to the extent that they are necessary to meet a particular mixdesign requirement.

Notably, the exemplary pollution control device 14 shown in FIGS. 4 and5 can be provided with tubes 160 that have an exemplary total outsidefiber bed surface area of about 1,296 square feet and can also beprovided with an exemplary clean air output rate of about 12,000 actualcubic feet per minute (ACFM) at about 120 degrees F., without exceedingthe foregoing dimensional limitations that permit conventional truckingof the pollution control device 14. This clean air output rate can beachieved, for example, when the emissions from the rotary dryer 12 areprovided at a rate of 6,265 standard cubic fee per minute (SCFM) and ata temperature of about 200 degrees F. and when ambient air is introducedvia the air introduction port 112 at a rate of about 5,144 ACFM atambient temperature. Within the foregoing dimensional limitations and atthe indicated flow rates, the clean air output from the pollutioncontrol device 14 advantageously can be provided with an opacity of lessthan or equal to about 5%. Notably, the fiber bed filter life can be 6months or as high as one year or more, even if the rotary dryer 12 isused about 8 hours per day.

As shown in FIGS. 4 and 5, the housing 166 can be provided with severalaccess hatches 200 or doors 202. The access hatches 200 or doors 202 canbe used to gain access to the contents of the housing 166, for example,when the fiber bed filter 90 is to be replaced or when maintenance orrepair of the internal components becomes necessary or desirable.

The pollution control device 14 can be configured to handle as much as20,000 ACFM of total flow, without exceeding the aforementioneddimensional limitations. This represents a significant advance,especially since the foregoing performance (i.e., an opacity less thanor equal to 5%) is achieved even when the emissions are high inhydrocarbon content, as is typically the case when the emissions arefrom a rotary drying process carried out on primary ingredientsconsisting of 100% RAP or commingled RAP with virgin aggregates. Whileother pollution control devices might be able to handle flow ratesgreater than or equal to 20,000 ACFM, without exceeding theaforementioned dimensional limitations, those other devices typicallycannot provide the desired opacity of less than or equal to 5% when 100%RAP is introduced into the rotary dryer 12 or when virgin aggregates arecommingled with the RAP during introduction into the rotary dryer 12.The hydrocarbon emissions from such RAP processing tends to overwhelm orotherwise exceed the capabilities of the other pollution controldevices. Some of the other compact pollution control devices also sufferfrom one or more of the aforementioned disadvantages, such as excessivecomplexity, excessive maintenance requirements (labor intensive,frequent servicing, and/or expensive to maintain), and/or excessivecosts to implement and operate.

Preferably, the fan 180/damper 182 combination and/or theadjustable-speed fan and the associated ducts are adapted to provide apressure drop across the fiber bed filter 90 of about 4 to 5 inchesv/ater column (W.C.) when the fiber bed filter 90 is clean (or new), anda pressure drop of about 12 inches W.C. when it is time to change thefiber bed filter tubes 160. This advantageously provides a relativelylong filter life (e.g., from 6 months between filter changes to as muchas one year or more). The exemplary starting pressure range of about 4-5inches W.C., when combined with the typical fan 180 capabilities of upto about 21 inches W.C. also is compatible v/ith the Dperatingcharacteristics of the cooling zone 92 and its particulate filteringcapabilities.

Generally, based on an exemplary inside diameter of each filter tube 160of about 4 inches, it is desirable to keep the operating velocity (i.e.,the flow rate in ACFM divided by the filter surface area) of the cleanair through the filter tubes 160 at or below 40 FPM. When the velocityremains at or below 40 FPM, the exemplary filter tubes 160 operate at ahigh filtering efficiency. Generally/the fiber bed filter 90 should beused in the high efficiency velocity range associated with the insidediameter of the filter tubes 160. The foregoing total flow rate of12,000 ACFM at 120 degrees F. can be provided with a velocity of about17 FPM, which is well within the high efficiency velocity range of theexemplary fiber bed filter 90.

The exemplary embodiment of the pollution control device 14 shown inFIGS. 4 and 5 also includes a temperature sensor T1, a fire detectorFDI, a low sump water level switch LSL, a high sump water level switchHSL, a make-up water valve WV, differential pressure transmitters DPI, avisible water level gauge (e.g., a float gauge U), and a recirculationv/ater pressure sensor PIC. The temperature sensor T1 provides a signalindicative of the temperature at the inlet 192 to the pollution controldevice 14. The fire detection sensor FDI is located at the inlet 192 tothe pollution control device 14. The output from the fire detectionsensor FDI can be used to initiate a fire response protocol when thesignal indicates that a fire has been detected. The high and low sumpwater level switches HSH, LSL can be used to activate and deactivate, orcontrol the speed of the recirculation pump 130 in a manner dependentupon the water level in the coolant recovery mechanism (or sump) 110.The make-up water valve WV can be controlled to selectively open andclose to compensate for losses of the coolant (e.g., water) 100 toevaporation. The differential pressure transmitters DPI can be used toprovide diagnostic and/or control signals regarding operation ofrespective segments of the pollution control device 14. The visiblewater level gauge U, such as a float gauge, can be located on an outsidesurface of the pollution control device's housing 166 to provide areadily accessible and visible indication of the coolant (e.g., water)level in the coolant recovery mechanism (or sump) 110. The recirculationwater pressure sensor PIC is adapted to indicate whether there is waterpressure in the coolant recirculation lines.

While other dimensions can be provided, a preferred implementation ofthe hot mix asphalt manufacturing system illustrated in FIGS. 1-12 hasthe following dimensional characteristics.

The entire rotary drum structure preferably is mounted on a frame 210(shown in FIGS. 2 and 3) that is no longer and wider than theaforementioned dimensional limitations to conventional trucking. Theframe 210 therefore can be incorporated into, or mounted on, a trucktrailer. The entire rotary dryer 12 and its associated ducts andequipment preferably extends no higher than 11 feet, 6 inches from thetop of the frame 210.

The rotatable drum 18 of the rotary dryer 12 preferably has a diameterof about 72 inches and a length of about 25 feet. The combustion chamber28 preferably has a diameter of about 36 inches and a length of about 46inches. The circumferential walls 42 of the combustion chamber 28 areabout ¼ inch thick and are about 9 to 18 inches away from the insidecircumferential wall 30 of the rotatable drum 18. The heat shield 40 canbe provided with a diameter of about 22 inches and a thickness of about¼ inch.

The deflector plate 58 preferably is about 6 inches away from the top212 of the inside circumferential surface 214 of the combustion chamber28 and is about 4 inches away from the forward wall 216 of therecirculation transition duct 54. The deflector plate 58 preferablyextends about 8 inches into the combustion chamber 28 and about 8 inchesinto the recirculation transition duct 54. The recirculation transitionduct 54 preferably provides a width reduction from about 22 inches toabout 16 inches, and a length expansion of from about 22 and ⅝ inches toabout 36 inches. The recirculation transition duct 54 has a height ofabout 12 inches.

The recirculator duct 46 preferably has a diameter of about 24 inches.The plate collector 70 preferably has a width of about 40 inches, aheight of about 36 inches, and a thickness of about 8 inches. Each plate72 in the plate collector 70 thus can have a width of about 8 inches anda length of about 36 inches. The separation between adjacent plates 72preferably is about one inch, thereby limiting the undulating flow path76 to a width of about one inch. The peak-to-peak undulationdisplacement of each plate 72 can be about one inch.

As shown in FIGS. 3, 10, and 11, the plate collector 70 preferably isdiagonally arranged inside the rotary dryer's exhaust duct 84. Thisperhaps is best illustrated in the top view of FIG. 11. The rotarydryer's exhaust duct 84 preferably is about 30 inches by about 37 inchesin cross-section. The bottom 218 of the exhaust duct 84 immediatelybefore the plate collector 70 preferably has a right-triangular opening220 that opens into the pollution control duct 86. The hypotenuse 222 ofthe right-triangular opening 220 preferably is slightly less than 40inches in length.

The pollution control duct 86 is connectable to the intake duct 192 ofthe pollution control device 14. Preferably, the entire pollutioncontrol device 14 is supported by a pollution control device frame 224.The pollution control device frame 224 is about 8 feet wide and about 37feet long. The frame 224 has an intake end 226 and a clean air exhaustend 228. The intake end 226 is where the recirculation pump 130 andmotor 132 are mounted for the coolant recovery mechanism 110 and wherethe intake duct 192 of the pollution control system 14 is carried.Preferably, the housing 166 is about 23 feet long, about 8 feet wide,and less than about 12 feet high. The cooling zone 92 occupies slightlyless than one quarter of the housing's length, closest to the intake end226 of the frame 224.

The remaining length of the housing 166 (closest to the clean airexhaust end 228) is occupied by the fiber bed filter 90.

A method of manufacturing hot-mix asphalt will now be described withreference to the exemplary rotary dryer 12 described above. Themanufacturing method includes the steps of providing a rotary dryer 12and at least one pollution control device 14 with dimensions that permituse of conventional trucking to transport the rotary dryer 12 andpollution control device 14 in less than three conventional truck-loads,feeding primary ingredients of hot-mix asphalt into the rotary dryer 12,drying the primary ingredients of hot-mix asphalt in the rotary dryer12, and treating emissions from the rotary dryer 12 so that hydrocarbonsand particulates are substantially removed from the emissions of therotary dryer 12 before such emissions are released into a surroundingenvironment of the rotary dryer 12.

To stay within the aforementioned dimensions limits, the rotary dryer 12and pollution control device 14 can be configured so that each haslength that is less than or equal to about 53 feet, a height that isless than or equal to about 13 feet, 6 inches, and a width is less thanor equal to about 8 feet, 6 inches.

Preferably, the step of drying the primary ingredients is performed in acounter-flow manner, and the method further comprises the steps ofrecirculating emissions from the rotary dryer 12 back into a combustionchamber 28 of the rotary dryer 12 and removing particulates, using theplate collector 70, from the emissions that are recirculated back intothe combustion chamber 28. The step of removing the particulates fromthe recirculated stream of emissions can include spraying of the platecollector 70 to clean away the collected particulates, as describedabove.

Preferably, the recirculation of emissions back to the combustionchamber 28 is performed so that the temperature of the counter-flowinggases is about 1,000 to 1,200 degrees F. as such gases exit from thecombustion chamber 28. The regulation of this temperature can beperformed by adjusting the speed of the recirculator fan 50 and/or bymodulating the position of the recirculation damper 48.

The step of drying the primary ingredients preferably includes the stepsof locating the combustion chamber 28 internally to the rotary dryer 12and protecting the primary ingredients from radiant heat produced in thecombustion chamber 28. Such protection, as indicated above, can beprovided using the heat shield 40 and walls 42 of the combustion chamber28.

Preferably, as indicated above, the step of providing the combustionchamber 28 includes the step of radially spacing the combustion chamber28 from an inside circumferential wall 30 of the rotary dryer 12, toprovide a mixing zone 32 between the combustion chamber 28 and theinside circumferential wall 30 of rotary dryer 12.

If desired, the method may further include the step of introducingsupplemental ingredients into the mixing zone 32 of the rotary dryer 12so that the supplemental ingredients are mixed with the primaryingredients after the primary ingredients have substantially completed adrying treatment in the rotary dryer 12. The supplemental ingredientscan include, for example, asphalt cement, rejuvinators, plasticizers, orcombinations thereof. Typically, the primary ingredients will havereached a temperature (e.g., about 300 degrees F.) by the time theyreach the mixing zone 32 that facilitates mixing of the supplementalingredients with the primary ingredients. The mixed supplemental andprimary ingredients then can exit the rotary dryer 12 through the outlet26 at or near the opposite end 22 of the rotary dryer 12.

The step of treating emissions from the rotary dryer 12 preferablyincludes passing the emissions through a fiber bed filter 90 to removehydrocarbons and particulates from those emissions. Preferably, theemissions are treated by subjecting them to coalescent filtration. Suchcoalescent filtration can include filtration by Brownian diffusion.

A second exemplary method of manufacturing hot-mix asphalt according tothe present invention will now be described. While this second methodcan be practiced using a rotary dryer 12 and/or pollution control device14 that satisfy the aforementioned dimensional constraints, it will beappreciated that it also can be practiced using rotary dryers 12 andpollution control devices 14 that do not satisfy the aforementioneddimensional limits.

This second method includes the step of providing a rotary dryer 12 withcertain characteristics. In particular, the rotary dryer 12 is providedwith 1) a rotatable drum 18 having a first end 20 and an opposite end22, 2) an inlet 24 for primary ingredients of hot-mix asphalt, the inlet24 being located at or near the first end 20 of the rotary dryer 12, 3)a combustion chamber 28 that is internal to the rotatable drum 18 of therotary dryer 12 and that is radially spaced apart from an insidecircumferential wall 30 of the rotatable drum 18, to provide a mixingzone 32 between the combustion chamber 28 and the inside circumferentialwall 30, and 4) a heat shield 40 adapted to protect the primaryingredients of hot-mix asphalt from radiant heat developed in thecombustion chamber 28.

In addition to providing the rotary dryer 12 with the foregoingcharacteristics, the second method further includes the steps of 1)introducing primary ingredients of hot-mix asphalt into the rotatabledrum 18, through the inlet 24, 2) rotating the rotatable drum 18 so thatthe primary ingredients are conveyed through the rotatable drum 18toward the opposite end 22 thereof, while combustion gases from thecombustion chamber 28 flow substantially from the opposite end 22 of therotary dryer 12 toward the first end 20 to heat and dry said primaryingredients, and 3) introducing supplemental ingredients into the mixingzone 32 of the rotary dryer 12 so that the supplemental ingredients aremixed with the primary ingredients after the primary ingredients havesubstantially completed a drying treatment in the rotary dryer 12.Preferably, as indicated above, the supplemental ingredients includeasphalt cement, rejuvinators, plasticizers, or combinations thereof.

The second method also preferably includes the step of recirculatingcombustion gases at the first end 20 back to the combustion chamber 28.As in the case of the first method, the second method can include thestep of using a plate collector 70 to remove particulates from thecombustion gases that are recirculated back to the combustion chamber28.

The emissions generated in the rotary dryer 12 by the second methodpreferably are treated so that hydrocarbons and particulates aresubstantially removed from such emissions before they are released intoa surrounding environment of the rotary dryer 12. This treatment of theemissions can be performed, as indicated above, by passing emissionsfrom the rotary dryer 12 through a fiber bed filter 90 to removehydrocarbons and particulates from the emissions. Preferably, theemissions are subjected to coalescent filtration when they are treated.Such coalescent filtration can include filtration by Brownian diffusion.

Preferably, the primary ingredients used in the second method include100% recycled asphalt products (RAP), or virgin aggregates commingledwith RAP. This advantageously takes advantage of the useful ingredientsin the RAP and conserves virgin aggregates. It also demonstrates theversatility of the second method. The second method is not limited touse with virgin aggregates only.

The present invention also provides a method of treating recirculatedgases in a hot-mix asphalt manufacturing system. This method can bepracticed, as indicated above, as part of the first and second exemplarymanufacturing methods and/or in conjunction with the exemplary systemshown in FIGS. 1-12, or alternatively, it can be practiced with otherhot-mix asphalt manufacturing methods and/or systems.

The method of treating recirculated gases comprises the steps ofdirecting recirculated gases from a rotary dryer 12 through a platecollector 70; and removing particulates from the recirculated gases asthe particulates are propelled, by the recirculated gases, into theplate collector 70. The step of removing particulates preferably isperformed so that at least about 90% of the particulates suspended inthe recirculated gases are removed therefrom.

Preferably, the method of treating recirculated gases further includesthe step of dislodging particulates that collect on the plate collector70 so that such particulates fall away from the plate collector 70without continuing with the recirculated gases. This can beaccomplished, for example, by spraying the plate collector 70 so that atleast some of the particulates removed by the plate collector 70 fromthe recirculated gases are cleaned away from the plate collector 70.Preferably, spraying of the plate collector 70 is performed using water,so that the water strikes the particulates and falls away from the platecollector 70, carrying at least some of the particulates away from theplate collector 70.

The method of treating recirculated gases also may include the steps ofdirecting excess gases that are not to be recirculated, to at least onepollution control device 14, and treating the excess gases at thepollution control device 14 so that hydrocarbons and particulates aresubstantially removed from the excess gases before such gases arereleased into a surrounding environment. Such treatment of the excessgases can be performed, as indicated above, by passing the excess gasesthrough a fiber bed filter 90 and/or by subjecting the excess gases tocoalescent filtration. Such coalescent filtration can include filtrationby Brownian diffusion.

Also provided by the present invention is a method of treating emissionsfrom a hot-mix asphalt manufacturing system. The emission treatmentmethod can be practiced, as indicated above, as part of the first andsecond exemplary manufacturing methods, as part of the aforementionedmethod for treating recirculated gases and/or in conjunction with theexemplary system shown in FIGS. 1-12. Alternatively, the emissiontreatment method can be practiced with other hot-mix asphaltmanufacturing methods and/or systems.

The emission treatment method comprises the steps of directing emissionsfrom a rotary dryer 12 to a fiber bed filter 90, and substantiallyremoving hydrocarbons and particulates from those emissions at the fiberbed filter 90 before such emissions are released into a surroundingenvironment of the rotary dryer 90. The hydrocarbons and particulatespreferably are substantially removed by subjecting the emissions tocoalescent filtration. Such coalescent filtration, as indicated above,can include filtration by Brownian diffusion.

Since the typical fiber bed filter will not operate properly when theemissions are provided to the fiber bed filter media at temperaturessignificantly higher than 120 degrees F., the emission treatment methodfurther comprises the step of cooling the emissions from the rotarydryer 12 enough that such emissions achieve a temperature that iscompatible with the fiber bed filter 90 before those emissions reach thefiber bed filter 90. The emission treatment method also may include thestep of introducing air that is cooler than the emissions into theemissions after the step of cooling to further cool the emissions priorto entering the fiber bed filter 90.

The step of cooling preferably includes spraying a coolant 100 throughthe emissions. An exemplary implementation of such spraying is thespraying of coolant (e.g., water) 100 in the cooling zone 92 shown inFIGS. 4 and 5. Preferably, the cooling step includes the step ofinducing a cyclonic flow of the emissions in a cooling zone 92, asdescribed above. This can be accomplished, for example, using thecyclonic plate 102 described above.

The step of cooling also may include the step of removing heat from thecoolant (e.g., water) 100 before the coolant 100 is sprayed through theemissions. The emission treatment method also preferably comprises thesteps of recovering coolant 100 that has been sprayed through theemissions, removing heat from recovered coolant 100 using a heatexchanger 118, and recirculating the coolant 100 by re-spraying thecoolant 100 through the emissions.

If the emission treatment method is practiced in conjunction with theaforementioned method for treating recirculated gases, the step ofspraying the plate collector 70 can be performed by spraying the platecollector 70 with the same coolant 100 (e.g., water) that is sprayedthrough the emissions as part of the emission treatment method. Thecoolant 100 sprayed onto the plate collector 70 also can be recoveredand recirculated by re-spraying that coolant 100 through the emissionsand/or also onto the plate collector 70.

The emission treatment method also can include the step of removingparticulates entrained in the coolant 100 from the coolant 100 prior tothe coolant 100 being re-sprayed through the emissions and/or onto theplate collector 70.

The emission treatment method described above preferably is performed onthe emissions from a rotary dryer 12 that is processing 100% recycledasphalt products, or virgin aggregates commingled with recycled asphaltproducts prior to or during introduction into the rotary dryer 12.

Notably, the aforementioned coalescent filtration and/or Browniandiffusion filtration can be used in the foregoing exemplary methods toprovide an exhaust opacity of less than or equal to about 5% even whenRAP-containing primary ingredients are being processed. This representsa significant advance over prior methods that would be overwhelmed orotherwise incapable of reliably providing an emissions opacity of 5% orless when RAP containing ingredients are processed.

In a preferred method of the invention, the products of combustion fromthe combustion chamber 28 are directed into the rotary dryer 12 and ontothe ingredients of the hot-mix asphalt without the introduction of any(or any substantial amount of) excess air and without the introductionof any (or any substantial) re-circulated exhaust gases, and without anyother steps intended to cool the products of combustion. Preferably therotary dryer 12 and combustion chamber 28 are operated at a slightlypositive pressure, such that the introduction of excess air isminimized.

Since no substantial amount of either excess air or re-circulated gasesis introduced into the rotary dryer 12, the heating gases that contactand heat the HMA ingredients within the rotary dryer 12 are atsubstantially the same temperature as the initial products of combustionfrom the combustion chamber 12.

A preferable fuel for the method is No. 2 heating oil that, with thepresent method, can produce initial products of combustion and heatinggases as high as 250° F. With the method of the present invention, and aheating gas inlet temperature of about 2100 to about 250° F., the outlet(i.e., exhaust) gas temperature may be about 200 to about 400° F. TheHMA ingredients, which may be comprised substantially entirely ofrecycled asphalt products, may obtain a maximum temperature of about 200to about 400° F. from an initial temperature typically equal to theambient temperature.

The heating of the HMA ingredients with high temperature heating gasescauses the release of a substantial amount of hydrocarbons from the HMA.The emissions are preferably treated in a manner that substantiallyremoves all particulates and hydrocarbons. As an example, the pollutioncontrol devices described above, including a pre-filter, cooling deviceand fiber filter may be advantageous.

HMA produced according to the present method has been found, mostunexpectedly, to possess highly desirable performance characteristics.In particular, under independent testing, HMA comprised of 100% RAP and0.6% rejuvenator produced according the method described immediatelyabove obtained a Performance Grade (PG) rating of PG 81-30, or PG 76-28,when determined by AASHTO Specification MP 1A, using Critical CrackingTemperature to define the low temperature grade, or when determined byAASHTO Specification MP1, using Creep Stiffness and m Value to determinelow temperature grade.

The tested product exhibited a temperature performance window of 10degrees Celsius (high+low temperature), which may be classified as an“excellent performer.” As a general rule, temperature performancewindows greater than or equal to 90 degrees Celsius usually require theaddition of a polymer modifier, which is costly and, therefore, noteconomically desirable.

While this invention has been described as having a preferred design, itis understood that the invention is not limited to the illustrated anddescribed features. To the contrary, the invention is capable of furthermodifications, usages, and/or adaptations following the generalprinciples of the invention and therefore includes such departures fromthe present disclosure as come within known or customary practice in theart to which the invention pertains, and as may be applied to thecentral features set forth above, and which fall within the scope of theappended claims.

What is claimed:
 1. A method of producing hot-mix asphalt comprising:introducing hot-mix asphalt ingredients into a counter-flow rotarydryer, said hot-mix asphalt ingredients including a substantial amountof recycled asphalt products; said recycled asphalt products flowing ina counter-flow direction; heating said hot-mix asphalt ingredients withheating gases from a combustion chamber, said heating gases having atemperature greater than 2100 degrees Fahrenheit, or said heating gasesnot including a substantial amount of excess air or a substantial amountof re-circulated gases such that said heating gases contact saidrecycled asphalt products at substantially a temperature of initialproducts of combustion of said combustion chamber; and directingemissions from said counter-flow rotary dryer through a pollutioncontrol device which substantially removes all particulates andhydrocarbons from said emissions.
 2. The method of claim 1, wherein saidhot-mix asphalt ingredients are comprised substantially entirely ofrecycled asphalt products.
 3. The method of claim 2, wherein saidheating gases having a temperature greater than 2100 degrees Fahrenheitand not including a substantial amount of excess air or a substantialamount of re-circulating gases.
 4. The method of claim 2, wherein: saidpollution control device includes a pre-filter, a cooling device and afiber bed filter; and said emissions are directed through saidpre-filter and said cooling device prior to said fiber bed filter. 5.The method of claim 2, wherein said pollution control device performscoalescent filtration.
 6. The method of claim 1, wherein: said pollutioncontrol device includes a pre-filter, a cooling device and a fiber bedfilter; and said emissions are directed through said pre-filter and saidcooling device prior to said fiber bed filter.
 7. The method of claim 1,wherein said pollution control device performs coalescent filtration. 8.A method of manufacturing hot mix asphalt, comprising: introducing intoa counter-flow rotary dryer a mixture of dry ingredients includingcommingled recycled asphalt products and virgin aggregates,pre-filtering emissions from the rotary dryer to remove particulates,cooling the emissions of the rotary dryer, filtering the emissions fromthe rotary dryer with a fiber bed filter to substantially removehydrocarbons before such emissions are released into a surroundingenvironment of the rotary dryer, wherein the steps of pre-filtering andcooling the emissions of the rotary dryer occur prior to the step offiltering the emissions.
 9. A method of manufacturing hot mix asphalt,comprising: introducing into a counter-flow rotary dryer dry ingredientscomposed of 100% recycled asphalt products, pre-filtering emissions fromthe rotary dryer to remove particulates, cooling the emissions of therotary dryer, filtering the emissions from the rotary dryer with a fiberbed filter to substantially remove hydrocarbons before such emissionsare released into a surrounding environment of the rotary dryer, whereinthe steps of pre-filtering and cooling the emissions of the rotary dryeroccur prior to the step of filtering the emissions.
 10. A method ofproducing hot-mix asphalt comprising: introducing hot-mix asphaltingredients into a counter-flow rotary dryer, said hot-mix asphaltingredients including a substantial amount of recycled asphalt products;heating said hot-mix asphalt ingredients with heating gases from acombustion chamber, said heating gases having a temperature greater than2100 degrees Fahrenheit, or said heating gases not including asubstantial amount of excess air or a substantial amount ofre-circulated gases such that said heating gases contact said recycledasphalt products at substantially a temperature of initial products ofcombustion of said combustion chamber; directing emissions from saidcounter-flow rotary dryer through a pollution control device whichsubstantially removes all particulates and hydrocarbons from saidemissions; said pollution control device includes a pre-filter, acooling device and a fiber bed filter; and said emissions are directedthrough said pre-filter and said cooling device prior to said fiber bedfilter.
 11. The method of claim 10, wherein said hot-mix asphaltingredients are comprised substantially entirely of recycled asphaltproducts; said pollution control device includes a pre-filter, a coolingdevice and a fiber bed filter; and said emissions are directed throughsaid pre-filter and said cooling device prior to said fiber bed filter.